Lindskog, Stefan

Abstract [en]

Internet censorship in China is not just limited to the web: the Great Firewall of China prevents thousands of potential Tor users from accessing the network. In this paper, we investigate how the blocking mechanism is implemented, we conjecture how China's Tor blocking infrastructure is designed and we propose circumvention techniques. Our work bolsters the understanding of China's censorship capabilities and thus paves the way towards more effective circumvention techniques.

Winter, Philipp

Abstract [en]

Baksidestext

The Tor network was originally designed as low-latency anonymity network.However, as the years progressed, Tor earned a reputation as also being a useful tool to circumvent Internet censorship. At times, the network counted 30,000 users only from China. Censors reacted by tightening their grip on the national communication infrastructure. In particular, they developed techniques to prevent people from being able to access the Tor network. This arms race now counts several iterations and no end is in sight.

This thesis contributes to a censorship-resistant Tor network in two ways. First, it analyses how existing censorship systems work. In particular, the Great Firewall of China is analysed in order to obtain an understanding of its capabilities as well as to explore circumvention opportunities. Second, this thesis proposes practical countermeasures to circumvent Internet censorship. In particular, it presents a novel network protocol which is resistant to the Great Firewall's active probing attacks.